1. Technical Field of the Invention
The present invention relates to automotive alternators for use in, for example, passenger cars and trucks.
2. Description of the Related Art
Japanese Patent First Publication No. 2001-86706 discloses an automotive alternator which includes a built-in rectifier. The rectifier has diodes serving as rectifying elements and terminals for making electric connection between the diodes. The terminals are also connected to a stator winding of the alternator. Further, to effectively dissipate heat generated by the diodes, the terminals are made of a metal having high heat conductivity, such as copper or a copper alloy.
However, when the stator winding is made of a metal other than copper and copper alloys, it is impossible to easily join, for example by welding, lead portions of the stator winding to the terminals of the rectifier during assembly of the alternator.
Japanese Patent First Publication No. 2007-20302, an English equivalent of which is US 2007/0007843 A1, discloses an automotive alternator where the majority of a stator winding is made of aluminum with the remainder, including lead wires, made of copper. With such a configuration, the lead wires of the stator winding can be easily joined to the copper-made terminals of a rectifier of the alternator, without increasing the manufacturing cost of the alternator.
However, in the stator winding, the joining between the majority made of alumina and the remainder made of copper is a bimetallic joining; therefore, electrolytic corrosion may easily occur around the joining portions due to the difference in self potential between the majority and reminder of the stator winding, thereby lowering the strength of the stator winding.